Earth's Strange Tango With the Sun

By: Phil Berardelli
By: Phil Berardelli

Every few minutes, short-lived portals open on the dayside of Earth's magnetic field, new satellite observations reveal. During that time, Earth and the sun are locked in a magnetic tangle that could trigger the geomagnetic storms that occasionally bedevil satellite communications and electrical power systems on the ground.
The space between Earth and the sun may look as empty as the voids between the stars, but a lot is going on there. Even on its quietest days, the sun emits enormous numbers of charged particles that strike Earth's protective magnetic field. Sometimes, that interaction becomes visible in beautiful, illuminated displays such as the Northern Lights, as the particles flow along magnetic field lines toward Earth's poles. But much of the Earth-sun interplay is subtler. Previous satellite data had revealed the existence of so-called flux-transfer events (FTEs), which create direct, magnetic connections between Earth and the sun. However, until now scientists had not observed the phenomena in much detail.

New data collected by arrays of NASA and European satellites have shown that FTEs are brief, intermittent, and erratic. One way to think about FTEs is to "imagine a straw poking through a soap bubble and connecting the air on both sides," says space scientist David Sibeck of NASA's Goddard Space Flight Center in Laurel, Maryland, who has submitted a paper on the phenomena to Annales Geophysicae. During the several minutes an FTE exists, our planet is magnetically entangled with the sun. The implications of this connection remain unknown, but it could channel much larger amounts of high-energy solar particles toward Earth.

There's "so much we don't know about them: what triggers them, how big they are, which way they move, where they go, and how they disintegrate--or even if they disintegrate--as well as what their shape is," says Sibeck. Whatever they turn out to look like, he says, they're bound to reveal more about the way particles in the solar wind enter Earth's magnetosphere to power geomagnetic storms.

Those storms can damage communications satellites and power grids, "but they wouldn't occur if the magnetic field hadn't built up the energy in the first place," says space scientist Robert Fear of the University of Leicester in the U.K. "It may well be that FTEs are the main source of the buildup," he says, but no one knows whether they play a small or large part in the process.

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